Direct Transformation of SiH to a Molecular L(H)Co═Si═Co(H)L Silicide Complex.

The synthesis of bimetallic molecular silicide complexes is reported, based on the use of multiple Si-H bond activations in SiH at the metal centers of 14-electron LCo fragments (L = Tp″, HB(3,5-diisopropylpyrazolyl); [BPPz], PhB(CHPBu)(pyrazolyl)). Upon exposure of (Tp″Co)(μ-N) () to SiH, a mixture of (Tp″Co)(μ-H) () and (Tp″Co)(μ-H) () was formed and no evidence for Si-H oxidative addition products was observed. In contrast, [BPPz]-supported Co complexes led to Si-H oxidative additions with the generation of silylene and silicide complexes as products. Notably, the reaction of ([BPPz]Co)(μ-N) () with SiH gave the dicobalt silicide complex BPPzCo═Si═Co(H)[BPPz] () in high yield, representing the first direct route to a symmetrical bimetallic silicide. The effect of the [BPPz] ligand on Co-Si bonding in and was explored by analysis of solid-state molecular structures and density functional theory (DFT) investigations. Upon exposure to CO or DMAP (DMAP = 4-dimethylaminopyridine), converted to the corresponding [BPPz]Co(L) adducts (L = CO, = 2; L = DMAP, = 1) with concomitant loss of SiH, despite the lack of significant Si-H interactions in the starting complex. On heating to 60 °C, underwent reaction with MeCl to produce small quantities of MeSiH ( = 1-3), demonstrating functionalization of the μ-silicon atom in a molecular silicide to form organosilanes.